This invention relates to the deployment of endoluminal prostheses and, more particularly, to an improved multi-sheath delivery catheter for such deployment.
Endoluminal prostheses are used for reinforcing or repairing blood vessels and other lumens within the body. For example, arteries narrowed or occluded by stenosis, thrombosis, or aneurysm may be reinforced, with or without additional surgical procedures such as angioplasty, by placing a prosthesis in the diseased portion of the artery. Such prostheses may be deployed within a body lumen by minimally invasive endoluminal insertion techniques. These include xe2x80x9csurgical cut-downxe2x80x9d procedures in which a small incision is made in the vasculature, for example in the femoral artery in the leg or in an artery in the shoulder of a patient, and a catheter is inserted at that location into the vessel. The catheter is maneuvered to the desired point of deployment, and the prosthesis is advanced through the catheter to that point. During this insertion process, the prosthesis is in a reduced diameter configuration, smaller than its intended diameter for use in repairing the vessel. The prosthesis is then expelled from the catheter into the vessel and expanded, with or without additional manipulation, into its intended use diameter within the vessel. The catheter is then removed from the body. Alternatively, percutaneous access may be used, wherein a needle puncture rather than a surgical incision is used to gain access to the vasculature. Percutaneous techniques are used for inserting relatively small prostheses; surgical cut-down techniques are used for relatively large ones.
A typical known insertion catheter consists of an outer sheath having a pusher slidably disposed within it. See, for example, U.S. Pat. No. 5,405,377 to Cragg. Once the catheter is inserted in the vessel and the prosthesis is advanced to the desired location within the vessel, the pusher is held in place while the outer sheath is retracted. This effectively discharges the prosthesis from the catheter.
For some prostheses, this simple pusher-in-sheath catheter arrangement is insufficient. An example of such a prosthesis is one having multiple diameters along its axis, such as the bifurcated prosthesis described in U.S. Pat. No. 5,609,627 to Goicoechea et al. The bifurcated prosthesis described in that patent has a stent portion having a first diameter adapted to be disposed in an aorta, and a branch portion having a second diameter, smaller than the first diameter, that extends into one of the iliac arteries. To insert such a multi-diameter stent, a multi-sheath delivery catheter is required.
It is also occasionally necessary to use a multi-sheath catheter to deliver a conventional straight prosthesis. With some prostheses, significant frictional forces exist between the prosthesis and the outer sheath of the catheter in which it is contained for transport to the delivery location and deployment. This may be the case with relatively long prostheses because friction increases as the outer surface area of the prosthesis increases.
A known multi-sheath delivery catheter 10 is illustrated in FIG. 1. Multi-sheath catheter 10, similar to that disclosed in Goicoechea ""627, comprises outer sheath 11, middle sheath 12, and pusher 13. Outer sheath 11 and middle sheath 12 are designed to be of an optimum diameter for containing the aortic portion and one bifurcated leg portion, respectively, of the bifurcated stent described above.
Outer sheath 11, middle sheath 12, and pusher 13 are concentrically slidably disposed relative to one another and are diametrically sized such that the prosthesis does not buckle against pusher 13 during deployment. In order to deploy a prosthesis contained within outer sheath 11 and middle sheath 12, catheter 10 is first percutaneously inserted to the desired delivery location within a body lumen according to methods known in the art. Outer sheath 11 is then retracted while middle sheath 12 and pusher 13 are held stationary. This action releases the first portion of the prosthesis that had been contained by outer sheath 11 because stationary middle sheath 12 and pusher 13 effectively prevent the first and second portions, respectively, of the prosthesis from moving as outer sheath 11 is retracted. Outer sheath 11 and middle sheath 12 are then retracted together while pusher 13 is held stationary to complete deployment of the prosthesis.
During this deployment, it is important that the tubes do not rotate with respect to one another. Rotation of any one of the tubes independently along its axis will not rotate the others. Such rotation could cause twisting or misalignment of the prosthesis being delivered. This also makes it difficult to gauge the twist or orientation of the prosthesis within the catheter, which is critical for aligning bifurcated prostheses with the anatomy. In addition, if the concentric tubes described above are not withdrawn in the proper order, the system will not properly deploy the prosthesis. Care must thus be exercised by a physician using a multi-sheath catheter to implant a prosthesis to retract the tubes in proper order.
An improved multi sheath delivery catheter for deployment of endoluminal prostheses is desired.
In a first aspect, the present invention provides a multi-sheath delivery catheter for introducing a prosthesis into a body lumen that has (a) an outer sheath adapted to contain a portion of the prosthesis and having an inner surface with a non-round cross-section; (b) a middle sheath slideably disposed at least partly within the outer sheath and adapted to contain another portion of the prosthesis, the middle sheath having a distal end with a first handle attached to it that has a non-round cross-section corresponding to and engaging the non-round cross-section of the inner surface of the outer sheath; and (c) a pusher slideably disposed at least partly within the middle sheath and adapted to engage the prosthesis; whereby relative rotational movement between the outer sheath and the middle sheath is prevented by virtue of the engagement of the non-round cross-section of the first handle with the non-round cross-section of the inner surface of the outer sheath. The pusher has a distal end with a second handle attached to it that has a non-round cross-section corresponding to and engaging the non-round cross-section of the first handle, whereby relative rotational movement between the pusher and the middle sheath is prevented by virtue of the engagement of the non-round cross-section of the second handle with the non-round cross-section of the first handle.
In another aspect, the invention provides a method for introducing a prosthesis to a body lumen using a multi-sheath delivery catheter having an outer sheath with an inner surface, a middle sheath having a distal end and being slideably disposed at least partly within said outer sheath, and a pusher having a distal end and being slideably disposed at least partly within said middle sheath. The method includes the steps of (a) forming a non-round cross-section in the inner surface of the outer sheath; and (b) attaching to the distal end of the middle sheath a handle that has a non-round cross-section corresponding to and engaging the non-round cross section formed in the inner surface of the outer sheath. The method also includes the step of attaching to the distal end of the pusher a handle that has a non-round cross-section corresponding to and engaging the non-round cross section of the middle sheath.
In another aspect, the invention provides a delivery catheter having a plurality of concentric tubes including an outer tube with an inner surface and an inner tube with an outer surface, at least one of which tubes is adapted to contain at least a portion of the prosthesis, and a first protrusion on the inner surface of the outer tube and a second protrusion, adapted to engage the first protrusion, on the outer surface of the inner tube, wherein the outer tube is adapted to be retracted over the inner tube before engagement of the first and second protuberances, and the outer tube and the inner tube are adapted to be retracted together upon the engagement.
In another aspect, the invention provides a delivery catheter having a plurality of concentric tubes including an outer tube having a distal end and an inner surface and an inner tube having a periphery, at least one of which tubes is adapted to contain at least a portion of the prosthesis during introduction to the body lumen, and (a) at least one notch on the inner tube; (b) a prong assembly disposed on the periphery of the inner tube and abutting the distal end of the outer tube, the prong assembly having at least one prong adapted to engage the notch in the inner tube; (c) a lock ring having a first portion adapted to be disposed over the distal end of the outer tube and a second portion adapted to be disposed over the prong assembly abutting the distal end; and (d) a protrusion on the inner surface of the outer tube; wherein the second portion of the lock ring is adapted to exert a force on the prong assembly sufficient to maintain the engagement of the prong with the notch and thereby prevent relative axial movement of the inner and outer tubes.
In another aspect, the invention provides a delivery catheter having a plurality of concentric tubes including an outer tube having a distal end and an inner tube having a periphery. The catheter also has (a) at least one notch on the inner tube; (b) a cam-lock assembly having (i) a hub fixedly attached to the distal end of the outer tube; and (ii) a cam-lock knob rotationally attached to the hub around the periphery of the inner tube; (iii) the cam-lock knob having a detailed inner cam surface adapted to engage the notch in a first position, thereby preventing relative axial motion between the inner and outer tubes, and disengaging the notch in a second position, thereby permitting relative axial motion between the inner and outer tubes.
In another aspect, the invention provides a delivery system for introducing a prosthesis to a body lumen including (a) a guidewire; (b) a catheter with a lumen adapted to slide over said guidewire, a proximal end, an interior, and a plurality of concentric tubes, at least one of which is adapted to contain at least a portion of the prosthesis during introduction to the body lumen; and (c) a nose cone disposed around the guide wire at the proximal end of the catheter, the nose cone having a hole formed through it that is adapted to communicate with both the interior of the catheter and an ambient environment before insertion of the nose cone into the body lumen; whereby the hole allows flushing of the catheter to remove air bubbles from the catheter before insertion into the body lumen.
In another aspect, this invention provides a method for preventing leakage of fluid from an interior of a delivery catheter by disposing the outer tube on a mandrel having a cross-sectional area substantially equivalent to that of the inner tube, applying a compressive force to a portion of the outer tube, heating the outer tube to shrink it around the mandrel, and assembling the outer tube concentrically over the inner tube such that a seal is created between the portion of the outer tube and the inner tube.